Abstract: The scarcity of natural sand  in shield tunneling leads to higher construction costs. To promote energy conservation, reduce emissions, and protect the environment, the authors develop a novel shield tail synchronous grouting material that utilizes granite manufactured sand as a fine aggregate. Laboratory and microscopic testing methods are employed to evaluate the properties of the grout. First, granite mortar with varying fineness moduli is prepared, which allows us to investigate how the grading of manufactured sand affects the properties of the grout. Second, the basic performance parameters of the novel material are tested and the grout ratio is optimized through orthogonal experiments and regression analysis. Finally, the microstructure and internal structure of the grout solid block are analyzed using scanning electron microscopy. The results reveal the following: (1) The novel grouting material exhibits high late strength, a rapid setting time, good fluidity, a low bleeding rate, and minimal consolidation shrinkage. (2) When the fineness modulus of the granite manufactured sand is between 2.6 and 3.0, the grout strength is significantly enhanced, and bleeding and shrinkage rates remain at acceptable levels. (3) The optimal performance is achieved with a granite sand fineness modulus of 3, water-binder ratio (water/cementitious material) of 0.8, cementitious sand ratio (sand/cementitious material) of 1.0, swelling ratio (bentonite/cementitious material) of 0.15, and ash powder ratio (cement/fly ash) of 0.8. This composition results in a three-day compressive strength of 0.92 MPa, 28-day compressive strength of 6.1 MPa, fluidity of 23 cm, consistency of 12.5 cm, bleeding rate of 2.5%, and consolidation shrinkage rate of 4.0%, all of which outperform traditional grout.

Key words: shield tunnel, manufactured sand, granite, synchronous grouting material, laboratory test, scanning electron microscopy